Thermally degradable polymeric fibers

Abstract

A microvascular system includes a solid polymeric matrix and a woven structure in the matrix. The woven structure includes a plurality of fibers, and a plurality of microfluidic channels, where at least a portion of the microfluidic channels are interconnected. The microvascular system may be made by forming a composite that includes a solid polymeric matrix and a plurality of sacrificial fibers in the matrix, heating the composite to a temperature of from 100 to 250° C., maintaining the composite at a temperature of from 100 to 250° C. for a time sufficient to form degradants from the sacrificial fibers, and removing the degradants from the composite. The sacrificial fibers may include a polymeric fiber matrix including a poly(hydroxyalkanoate) and a metal selected from the group consisting of an alkali earth metal and a transition metal, in the fiber matrix, where the concentration of the metal in the fiber matrix is at least 0.1 wt %.

What is claimed is: 
     
       1. A method of making a microvascular system, comprising:
 forming a composite comprising:
 a solid polymeric matrix, and 
 a plurality of sacrificial fibers having a degradation temperature of from 180 to 250° C. in the polymeric matrix;
 where the sacrificial fibers comprise a poly(hydroxyalkanoate) and at least 0.1 wt % of a metal compound selected from the group consisting of a tin salt of a mono- or di-carboxylic acid, and scandium triflate (Sc(OTf) 3 ); 
 
 
 heating the composite to a temperature of from 100 to 250° C.; 
 maintaining the composite at a temperature of from 180 to 250° C. for a time sufficient to form degradants from the sacrificial fibers; and 
 removing the degradants from the composite to provide the microvascular system. 
 
     
     
       2. The method of  claim 1 , where the forming of the composite comprises:
 contacting the sacrificial fibers with a non-solid polymeric matrix precursor; and 
 solidifying the polymeric matrix precursor to form the composite comprising the sacrificial fibers in the solid polymeric matrix. 
 
     
     
       3. A method of making a microvascular system, comprising:
 forming a composite comprising:
 a solid polymeric matrix, and 
 a woven structure in the polymeric matrix, the woven structure comprising a plurality of reinforcing fibers, and a plurality of sacrificial fibers having a degradation temperature of from 180 to 250° C.; 
 
 where the sacrificial fibers comprise a poly(hydroxyalkanoate) and at least 0.1 wt % of a metal compound selected from the group consisting of a tin salt of a mono- or di-carboxylic acid, and scandium triflate (Sc(OTf) 3 ); 
 heating the composite to a temperature of from 100 to 250° C.; 
 maintaining the composite at a temperature of from 180 to 250° C. for a time sufficient to form degradants from the sacrificial fibers; and 
 removing the degradants from the composite to provide the microvascular system. 
 
     
     
       4. The method of  claim 3 , where the woven structure comprises warp threads and weft threads in two dimensions, and at least a portion of the sacrificial fibers are present as weft threads. 
     
     
       5. The method of  claim 3 , where the woven structure comprises warp threads, weft threads and Z-threads in three dimensions, and at least a portion of the sacrificial fibers are present as weft threads or Z-threads. 
     
     
       6. The method of  claim 3 , where the forming of the composite comprises:
 contacting the sacrificial fibers with a non-solid polymeric matrix precursor; and 
 solidifying the polymeric matrix precursor to form the composite comprising the woven structure in the solid polymeric matrix. 
 
     
     
       7. The method of  claim 3 , where at least a portion of the microvascular system comprises interconnected microfluidic channels. 
     
     
       8. The method of  claim 1 , where the sacrificial fibers have a degradation temperature of at most 220° C. 
     
     
       9. The method of  claim 1 , where the sacrificial fibers have a degradation temperature of at most 180° C. 
     
     
       10. A method of making a degradable polymeric fiber, comprising:
 combining:
 a fiber comprising a poly(hydroxyalkanoate), and 
 a composition comprising a fluorinated fluid and a metal compound selected from the group consisting of a tin salt of a mono- or di-carboxylic acid, and scandium triflate (Sc(OTf) 3 ); 
 
 maintaining the fiber and the composition together at a suitable temperature and for a time sufficient to provide a concentration of the metal compound in the fiber of at least 0.1 wt %; and 
 separating the fiber from the fluorinated fluid to form the degradable polymeric fiber having a degradation temperature of from 180 to 250° C. 
 
     
     
       11. The method of  claim 10 , where the poly(hydroxyalkanoate) comprises poly(lactic acid) (PLA). 
     
     
       12. The method of  claim 10 , where the tin salt of a mono- or di-carboxylic acid comprises tin(II) acetate, tin(II) oxalate or tin(II) octoate. 
     
     
       13. The method of  claim 10 , further comprising cold-drawing the degradable polymeric fiber. 
     
     
       14. The method of  claim 1 , where the metal compound has been incorporated in the sacrificial fibers by a process comprising infusion, liquid spinning, or melt spinning. 
     
     
       15. The method of  claim 3 , where the metal compound has been incorporated in the sacrificial fibers by a process comprising infusion, liquid spinning, or melt spinning. 
     
     
       16. The method of  claim 1 , where the metal compound has a concentration of at least 1 wt %. 
     
     
       17. A microvascular system prepared by the method of  claim 1 . 
     
     
       18. A microvascular system prepared by the method of  claim 3 . 
     
     
       19. The method of  claim 1 , where the poly(hydroxyalkanoate) comprises poly(lactic acid) (PLA). 
     
     
       20. The method of  claim 3 , where the poly(hydroxyalkanoate) comprises poly(lactic acid) (PLA).